1. Field of the Invention
The present invention generally relates to a measurement system, and more particularly to a dual mode measurement system using quartz crystal microbalance (QCM) to measure the mass and properties of an object to be measured.
2. Description of Related Art
Quartz crystal microbalance (QCM) is mainly used for measurement and sensing of trace substances, which has been applied in the field of biological sensor in recent years. Quartz is a piezoelectricity material, which is capable of performing energy conversion between mechanical energy and electric energy, which is called a piezoelectric effect. The piezoelectric sensors in the early stage, such as a surface acoustic wave (SAW) sensor, are mostly applied to measure contaminating materials in the air. The piezoelectric sensor has the characteristics of high sensitivity, high response speed, and portability, which thus is especially suitable for gas sensing in the relevant fields of public security, environmental protection, etc. Moreover, the piezoelectric crystal sensor has also been applied in vehicle tire pressure sensors, biological chips, and other fields.
A quartz sensing component applied in the QCM is generally clad with a layer of metal electrode, for example, gold electrode, for transmitting sub-signals. When the quartz sensing component generates physical deformation under a pressure, the resonance frequency of the quartz sensing component changes, and a tiny change for the mass of an object to be measured on the quartz crystal surface can be obtained based upon a variation relationship between the mass attached to the quartz crystal surface and the quartz oscillation frequency. The QCM deduces the change of the mass based on the variation of the frequency, and thus it has a relatively high sensitivity. If the frequency variation corresponding to each unit of mass change is several Hz, the sensitivity of the QCM reaches up to a level of 10−9 g for each unit of mass.
However, as for a biological sensor, it is rather insufficient to merely measure the mass of the object to be measured. If the biological sensor needs to analyze the quartz crystal AC impedance distribution and observe an acting force between the quartz surface and the carrier, so as to provide more messages in terms of the biological measurement, the object to be measured is must be moved to another measurement system, thereby increasing the measurement errors.